Entrances to Yellowstone National Park have been closed and visitors were evacuated after powerful rain and flooding washed away roads and triggered rockslides, the authorities said.
Millions of visitors each year are drawn to the wilderness and active geysers in Yellowstone, which is the oldest national park in the United States and sprawls across more than two million acres in the northwest corner of Wyoming and into Montana and Idaho. In 2021, more than 4.8 million people visited the park.
On Monday, the superintendent of the park, Cam Sholly, announced that its five entrances were closed to inbound traffic, at least through Wednesday, because of the “extremely hazardous” conditions. Video recorded from a helicopter showed a swollen river coursing along a collapsed, eroded roadway at the park’s northern entrance.
Visitors were evacuated from the northern section of the park, where there were multiple mudslides and where the roads and bridges have failed, Mr. Sholly said in a statement. Parts of the community of Gardiner, a hamlet of about 800 people that serves as the main northern entrance to the park, had no power or water and were receiving aid from the authorities in Montana, he said.
Mr. Sholly said the timing of the park’s reopening was uncertain until officials were able to assess the damage. “It is likely that the northern loop will be closed for a substantial amount of time,” he said.
Visitors in the southern portion of the park will also be evacuated, with forecasts of rising flood levels causing concern about water supplies and wastewater systems, said Mr. Sholly, who was named superintendent of the park in 2018.
Heavy rain on Sunday and snowmelt unleashed the flooding, which will continue to make its way through the river system on Tuesday through northwest Wyoming and southwest Montana, the National Weather Service said. Jason Straub, a meteorologist with the Weather Service, said 1.37 inches of rain fell on Sunday, according to measurements taken at Yellowstone Lake, beating a record of just under a half inch in 2005.
On Tuesday, Gov. Greg Gianforte of Montana declared a statewide disaster “due to flooding to help impacted communities get back on their feet as soon as possible.”
While cooler temperatures were forecast, slowing the pace of snowmelt, the region remained under a flood advisory through Tuesday, the Weather Service said. Thunderstorms and strong winds were forecast, mainly in northern Wyoming, and a chance of thunderstorms lingered for the rest of the week.
The unruly weather system has caused flooding that has spilled into the southwestern reaches of Montana, affecting residents in Park County, along the edge of the park.
Patients and staff at a hospital in Livingston, Mont., were evacuated on Monday as a precaution amid surging floodwaters, and emergency cases were diverted, the facility said. Residents in some parts of the county, including Livingston, were evacuated from homes, the authorities said.
“Travel is extremely limited and unsafe in many locations,” Park County emergency management authorities said in a statement. “Many bridges and roads are no longer operational. Many people are landlocked.”
In Paradise Valley, which connects Livingston to Gardiner on Yellowstone’s northern edge, residents watched as the Yellowstone River lapped at roads and took over properties in its path. A station where homeowners could fill sandbags was set up in the Park County fairgrounds.
“It’s a matter of life or death,” Christine Jupe, a Park County resident who was helping steer motorists away from the rising waters, told KBZK News, a television station in Bozeman, Mont.
Johnny Diaz contributed reporting.